This invention relates generally to methods for shipping cargo where the cargo requires ventilation. More specifically, the invention relates to methods for shipping cargo requiring ventilation in enclosed containers, such as container vans.
Various kinds of cargo is preferably shipped in the manner whereby the cargo is continuously ventilated by the circulation of ventilating gases. For example, where the cargo needs to be refrigerated, it is desirable to circulate chilled air throughout the cargo. Also, where the cargo consists of fresh produce, it is frequently desirable to circulate gaseous ripening agents and/or insecticides throughout the cargo.
Some produce, such as green bananas, emit gases as they ripen. Such gases tend to accumulate around the fruit. The gas generates additional heat which, in turn, tends to accelerate the ripening process (thereby causing the emission of additional gases). Accordingly, if the ripening gases are not sufficiently exhausted, the produce will ripen unduly rapidly and unevenly. Much of the produce may, thereby, become overripened and spoiled during shipment.
Most cargo is now shipped in container vans having approximately the size and shape of a conventional semi truck trailer. Shipment by such container vans is by far the most common method of shipping cargo on land, by sea and by rail. The popularity of shipping via container vans stems from the fact that such container vans can be conveniently loaded off-site from the transportation distribution center (harbor, railhead or truck distribution center) and transported all the way to the final destination via any one or more of several shipment modes (by sea, land or rail) without having to be unloaded and reloaded at each distribution center. Attempts to solve the need for ventilating certain cargo, therefore, revolves around methods of providing adequate ventilation within container vans.
The present industry standard for ventilating cargo within container vans is to place the cargo in boxes and to then stack the boxes, either individually or on pallet boards, within container vans having some form of perforated floor, such as a grating. After the cargo boxes are located into the container van, an attempt is made to circulate ventilation gases from the lower portion of the forward end wall of the container van, up through the perforated floor, and up through the boxes. The ventilation gases are then accumulated at the top of the container van and removed by a vacuum drawn at the upper portion of the forward wall.
This conventional method of ventilating container vans is not very effective. The problem is that once ventilating gases are injected into the floor of the container van at the forward end wall, the gases immediately begin rising up through cargo boxes at the forward end of the container van. Much of the ventilation gases passes rapidly around the boxes through vertical chambers formed in the loading process. Because so much of the ventilating gases leak upwardly through the vertical chambers at the forward end of the cargo load, little of the ventilation gases reaches the rearward end of the container van.
In U.S. Pat. Nos. 5,116,191 and 5,706,662, both of which are incorporated herein by this reference, two different methods are proposed to address the aforementioned problems. Both of these prior art methods, however, require the stacking of the cargo on pallet boards using special packing and retaining techniques, such that internal channels are generated within the cargo load. The use of such special stacking and retaining techniques, however, has not been well received in the industry. The industry continues to prefer to load boxes within container vans by simply stacking the boxes upon one another, either individually or on pallets, without having to employ the special stacking and retaining techniques.
Accordingly, there is a need for an improved method of shipping cargo requiring ventilation, which is adapted to the industry preference for avoiding special stacking and retaining techniques and which otherwise avoids the aforementioned problems in the prior art.
The invention satisfies this need. The invention is a method for shipping cargo in an enclosed, elongated cargo container van. The invention comprises the steps of (a) loading the cargo into boxes having a pair of opposed vertical side walls, a pair of opposed vertical end walls, a top wall and a bottom wall, (b) disposing the boxes in a plurality of tiers within the cargo container to form a cargo load having a top side and a bottom side, the boxes being disposed within the cargo container such that boxes in the forward portion of the enclosed space are tightly packed proximate to the sidewalls and to the forward end wall, the boxes being disposed within the cargo container so as to provide a plurality of vertical channels spaced apart from the side walls and spaced apart from the forward end wall, the vertical channels each extending from the bottom of the cargo load to the top of the cargo load, (c) disposing a baffle sheet horizontally across each vertical channel, at least some of the baffle sheets having one or more baffle sheet openings to allow the passage of gas through the baffle sheet, the number of baffle sheet openings in each baffle sheet being chosen so as to provide for a predetermined pressure gradient above the cargo load when a gas is circulated through the cargo load from the bottom of the cargo load to the top of the cargo load, and (d) commencing the circulation of a gas through the cargo load from the bottom of the cargo load to the top of the cargo load.